Your first question doesn't make much sense. That isn't an "or" situation - if you're drawing 2D sprites, all your animation is frame by frame.
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doppelgreenerNov 18 '12 at 1:55

I mean, the images frame by frame as a whole, not independent parts... (head, chest, arms)
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Edwin SohoNov 18 '12 at 3:14

Is going to be difficult to coordinate all the animations but basically i think that you should use one big CCSprite as the body and add each part as child of that body (all the parts could be CCSprites with their animations and properties). At least i how i resolve that...the you can color/change each part separately
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SetrioNov 20 '12 at 17:10

Check out Bootdisk Revolution. The blog goes over what you were asking. Animating Wryn Hope it helps!
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ManuelDec 14 '12 at 5:06

2 Answers
2

Different people will have different answers for you. The game
programmer & artist should collaborate, to determine the best
process of using sprites. OR you can design your sprites using
Layers, for each body part. That way you will have an original file
to refer back to, when you need to make modifications. Working with
Layers allows you to save each individual body part in a separate
file.

Again, different people will have different answers for you. I've
read several articles/blogs on the topic of Vector vs Bitmap. Best
approach I have read, is designing the original in Vector. This is
done because you can re-scale the image w/ no distortion, compared
with trying to re-scale an image in Bitmap. Final touches are made
and saved as Bitmap.

Remember OPINIONS are just that. You will have to determine the best process for YOUR game design. When you read articles/blogs remember to look at the author's background. Look for opinions from authors that are employed or previously employed by a company that makes games.

Using a plain ole sprite sheet and animating frame-by-frame works just fine. The same goes for doing skeletal animation. It's really going to come down to your specific needs, for instance:

Are there any particular technical contraints that make one option more attractive than the other? Frame-by-frame animations will tend to use more memory than skeletal ones. Skeletal animations will require more complex code to implement.

Are there any design constraints that make one option more attractive than the other? Do you want your character to bounce around like a rag doll when he dies? Do you need to be able to change the animation at runtime? These things will be easier to do with skeletal animation.

What tools does your artist prefer?

What workflow does your programmer like?

These are just a few questions to ask yourself and your team. You can probably come up with plenty more.

Whatever you do you definitely want to be exporting bitmaps for use in your game.